U.S. Pat. No. 7,141,297 discloses a multilayer polymeric mirror comprising oriented layers of PET alternating with layers of a PMMA/PVDF blend that has a Tg lower than the PET. That reference teaches:                “The amount of PVDF used in the blends is typically not more than about 40% by weight (i.e. a 60/40 PMMA/PVDF blend). With higher levels of PVDF, the miscibility of the PMMA and PVDF tends to deteriorate, thereby causing losses in clarity. In general, it is desirable to use PVDF in the blends in an amount as high as possible in order to increase the benefit in reductions in refractive index and glass transition temperature. However, smaller amounts can be used when it is desired to fine tune the composition to provide particular optical or physical properties for certain applications. For example, a 75/25 blend provides highly desirable physical and optical properties for use with high refractive index materials such as PEN, PET and mixtures or copolymers thereof” (U.S. Pat. No. 7,141,297 at col. 14, lines 42-55).        “As described above, the blending of polyvinylidene fluoride (PVDF) with PMMA reduces the glass transition temperature of the blended polymers. Preferably, the blend includes about 20 to 40 wt. % PVDF and 60 to 80 wt. % PMMA. Below about 20 wt. % PVDF, the glass transition temperature is above that of PET, although these blends are still acceptable for some applications. Above about 40 wt. %, PVDF crystallizes. The addition of PVDF to the second optical layers can also enhance other properties, such as, for example, solvent resistance.” (U.S. Pat. No. 7,141,297 at col. 14, line 65—col. 15, line 7.)        